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Evaluating Alfalfa Cutting As a Potential Measure to Enhance Predator Abundance of Aphis gossypii(Homoptera: Aphididae) in Cotton-alfalfa Intercropping System

刈割苜蓿助迁天敌对棉田棉蚜种群动态的影响研究



全 文 :第19卷 第6期
 Vol.19  No.6
草 地 学 报
ACTA AGRESTIA SINICA
   2011年  11月
  Nov.  2011
Evaluating Alfalfa Cutting As a Potential Measure to Enhance Predator
Abundance of Aphis gossypi (Homoptera:Aphididae)in
Cotton-alfalfa Intercropping System
CHEN Ming1.2,LUO Jin-cang2,LI Guo-qiang2
(1.Pratacultural Colege,Gansu Agricultural University,Lanzhou,Gansu Province 730070,China;
2.Institute of Plant Protection,Gansu Academy of Agricultural Sciences,Lanzhou,Gansu Province 730070,China)
Abstract:The effects of alfalfa-cutting and non alfalfa-cutting on the population dynamics of Aphis gossy-
pii Glover(Homoptera:Aphididae)and several species of arthropod predators were investigated in cotton-
alfalfa intercropping patterns of north-western China.The objectives of this study were to evaluate the
practicality of alfalfa-cutting as a management technique to enhance arthropod predator abundance of A.
gossypii.Plots consisted of 50-cm alfalfa strips intercropped with four-row cotton strips.Population den-
sity of A.gossypii was gradualy increased in cotton,cutting alfalfa twice on June and July forcing some
groups of predators to migrate into adjacent cotton fields from alfalfa.Individual number,species rich-
ness,and diversity of predators were higher in alfalfa-cutting treatments than that in non-cutting treat-
ments.The population density of Adonia variegata(Goeze)(Coleoptera:Coccinelidae),Pardosa varie-
gata L.Koch(Araneae:Lycosidae),Chrysopa sinica Tjeder(Neuroptera:Chrysopidae)and Orius minu-
tus(L.)(Hemiptera:Anthocoridae)increased 120.4%,100.8%,61.0%and 7.2%in alfalfa-cutting
treatments over that in non-cutting treatments.Meanwhile,the population density of A.gossypii in alfal-
fa-cutting treatments decreased 80.7% more than in non-cutting treatments.This indicates that alfalfa-
cutting induces predator immigration into adjacent cotton fields and helps control cotton aphids.This study
provides cotton growers a potential cultural management technique for A.gossypii while conserving preda-
tors.
Key words:Cotton-alfalfa intercropping;Alfalfa-cutting;Aphis gossypii;Arthropod predators;Popula-
tion dynamics
刈割苜蓿助迁天敌对棉田棉蚜种群动态的影响研究
陈 明1,2,罗进仓2,李国强2
(1.甘肃农业大学草业学院,甘肃 兰州 730070;2.甘肃省农业科学院植物保护研究所,甘肃 兰州 730070)
摘要:在棉苜间作模式下比较研究了刈割与非刈割苜蓿(Medicago sativa L.)对棉花(Gossypiumspp.)田几种主要
捕食性节肢动物和棉蚜(Aphis gossypii Glover)种群动态的影响,目的在于评价适时刈割苜蓿、助迁天敌对棉蚜的
控制效应。试验区每隔4行棉花间作1行50cm宽的紫花苜蓿带,当棉田棉蚜种群数量逐渐增高时,分别于6月、7
月2次刈割紫花苜蓿并搁置原地,迫使苜蓿带内的捕食性天敌转移到邻近的棉田中;设非刈割苜蓿处理为对照。
结果表明:刈割苜蓿后棉田内天敌种群的个体数、物种丰富度和多样性均较非刈割苜蓿处理区有明显的增加,其
中,多异瓢虫(Adonia variegata(Goeze))、星豹蛛(Pardosa variegata L.Koch)、中华草蛉(Chrysopa sinica Tjed-
er)、小花蝽(Orius minutus(Linn.))的种群数量分别增长120.4%,100.8%,61.0%和7.2%。刈割苜蓿处理区的
棉蚜种群数量比非刈割区下降了80.7%。在棉苜间作区,适时刈割苜蓿、助迁天敌转移至邻近棉田,有助于棉蚜的
控制。
关键词:棉苜间作;刈割苜蓿;棉蚜;捕食性节肢动物;种群动态
中图分类号:S435.622.1    文献标识码:A     文章编号:1007-0435(2011)06-0922-05
收稿日期:2011-05-11;修回日期:2011-10-08
基金项目:甘肃省科学事业费项目(QS031-C31-14)资助
作者简介:陈明(1957-),男,江苏张家港人,博士,研究员,主要从事农业昆虫和害虫综合治理研究,E-mail:cmppi@163.com
第6期 陈明等:刈割苜蓿助迁天敌对棉田棉蚜种群动态的影响研究
   The cotton aphid,Aphis gossypii Glover
(Homoptera:Aphididae),is a major pest of cotton
in China and in many other countries,especialy at
the seedling stage of cotton[1,2].High aphid densi-
ties have a negative impact on cotton yield and
could result in serious economic losses[3].
Natural enemy conservation and utilization are the
major control measures to cotton aphid[4~6].Relay in-
tercropping aids the early arrival and continuous popu-
lation increase of predators in cotton,thereby reducing
numbers and postponing the initial population increase
of the cotton aphid,compared to monoculture cotton
[7~9].Destructive sampling shows that predator move-
ment between cotton and sorghum was positively cor-
related with ambient temperatures and negatively cor-
related with local aphid levels [10].Some researchers
reported that a bordering alfalfa belt in cotton field
could efectively attract and reproduce predators of cot-
ton aphid[5,11,12].But this treatment increased distance
between cotton and alfalfa,probably influencing active
migration of predators from alfalfa field,and further-
more causing poor control efect to cotton pests.This
study evaluates a potentiality of alfalfa-cutting as a
management technique of enhanced arthropod predator
abundance of A.gossypi.
1 Materials and methods
1.1 Experimental sites
The experiment was carried out in cotton
fields of Dunhuang(E 94°38′,N 40°08′,1060m),
Gansu Province of China.The experiment site be-
longs to irrigated agriculture oases in typical conti-
nental arid climate zone,and annual mean tempera-
ture is 9.3℃,annual rainfal 36.8mm,annual
evaporation reaching 2490mm which is 67.7times
of annual rainfal.
1.2 Field experimental design
Alfalfa(Medicago sativa Linn.),was planted
in March in 2005and 2006.Dunmian-9916variety
of cotton was sown in April of 2005and 2006.Cot-
ton was planted 40cm apart with 16cm plant spac-
ing.Alfalfa strip(50cm-wide)was intercropped
with every four rows of cotton.The experiment in-
cluded alfalfa-cutting and non alfalfa-cutting treat-
ments.Each treatment plot was 333.3 m2 with
three replications in a completely randomized de-
sign.No pesticide was used during the sampling
stages in any treatments.Standard agronomic
practices for cotton and alfalfa field were used.Al-
falfa was cut on June and July when the population
density of cotton aphids gradualy increased in cot-
ton,and kept in their original place over one day.
1.3 Survey methods
The Chessboard sampling method[13] and
Sweep-net sampling method were applied for inves-
tigation.The survey was carried out at five days
interval from May to August of 2005and 2006.
There were ten sampling plots(1.6m×4m)
in the treatment.The species and numbers of
Arthropoda on the ground and the whole plant of
each plot were recorded.In particular,cotton a-
phids were counted on whole cotton plants before
July 1st and only counted on three true leaves from
the upper,middle,and lower parts of the main
stem after July 1st within the 100cotton plant cano-
pies.
Sweep-net sampling method consisted of three
sweep units used to sample insects taking flight
from the cotton surface.Each unit is 30sweeps
back and forth on sampling areas with a 33-cm-di-
ameter sweep-net.
Numbers of Cotton aphids and major natural
enemies were expressed as numbers per 1m2.
1.4 Data processing
Relative richness index,Pi=Ni/N,Nirepre-
sents the number of i species,and Nrepresents
the total number of whole species.Dominance in-
dex,d=Nmax/N,Nmaxrepresents the number of
dominant species.Richness index,R=S/ln(N),S
represents the number of species.Shannon-Wiener
index,H=-∑Piln(Pi).Evenness index,J=H/
ln(S)[13,14].
2 Results
2.1 Temporal patterns of predator community
At least 23species of arthropod predators
were colected in 2005and 2006,in which 20and
22species were insects and 3species of Arachnida.
The dominant groups of predators were Coccineli-
dae,Chrysopidae,Anthocoridae,and Lycosidae.
Figure 1shows temporal pattern tendency of
the individual numbers,richness,evenness and di-
versity index of predators in cotton-alfalfa inter-
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草 地 学 报 第19卷
cropping fields with alfalfa-cutting and non-cut-
ting.The individual number of predators increased
after alfalfa-cutting on June and July in cotton
fields.However the individual number of predator
did not change particularly in non alfalfa-cutting
plots during the entire examined period.The rich-
ness of predators in alfalfa-cutting plots was rela-
tive high.Predator population declined with cotton
aphid decrease after August.The evenness of
predators decreased rapidly after first and second
alfalfa-cutting due to predator migration from alfal-
fa to cotton,at the same time it decreased slowly
in non alfalfa-cutting plots.The diversity of the
predator community between alfalfa-cutting and
non-cutting plots showed little difference.
2.2 Population dynamics of cotton aphid and its
major predators
Figure 2shows population dynamics of Aphis
gossypii and the major predators in alfalfa-cutting
and non-cutting plots.The population density of
Adonia variegata (Goeze)(Coleoptera:Coccinel-
lidae),Pardosa variegata L.Koch(Araneae:Ly-
cosidae),and Chrysopa sinica Tjeder (Neurop-
tera:Chrysopidae)were higher in alfalfa-cutting
plots than in non-cutting plots during the entire
examined period.However,higher numbers of
Orius minutus(L.)(Hemiptera:Anthocoridae)in
alfalfa-cutting plots were not observed.The popu-
lation density of A.variegata,P.astrigera,C.
sinica and O.minutus in alfalfa-cutting plots in-
creased by 90.7%,134.0%,48.3%and 21.8%
after first cutting,and by 154.4%,51.1%,117.9%
and 1.2% after second cutting,and by 120.2%,
100.9%,61.1% and 6.8%during the experiment
period compared to non-cutting plots,respectively.
At the beginning of cotton aphid population
increase,cutting alfalfa twice on June and July
made predators of alfalfa strips migrate into cotton
fields resulting in predators increasing rapidly in
the cotton fields and had aphid population in cotton
controled longer.The population density of A.
gossypii in alfalfa-cutting plots decreased 80.7%
more than in non-cutting plots.It showed that cut-
ting alfalfa could attract predators migration into
cotton fields and reduce aphid population rapidly.
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第6期 陈明等:刈割苜蓿助迁天敌对棉田棉蚜种群动态的影响研究
3 Discussion and Conclusion
Habitat management is an ecologicaly based
approach aimed at favoring natural enemies and en-
hancing biological control in agricultural systems.
The goal of habitat management is to create a suit-
able ecological infrastructure within the agricultur-
al landscape to provide resources such as food for
adult natural enemies,alternative prey or hosts,
and shelter from adverse conditions.These re-
sources must be integrated into the landscape in a
way that is spatialy and temporaly favorable to
natural enemies and practical for producers to im-
plement[15].
Arthropod community ecology in crop fields is
a theoretical basis for IPM focusing on crops.Flea
beetles,Phyllotreta cruciferae Goeze,were more
abundant on colards (Brassica oleracea var.
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草 地 学 报 第19卷
acephala)grown in monocultures than on those
grown adjacent to natural vegetation [16].The re-
sult indicates that vegetation diversity can exert a
direct influence on populations of phytophagous in-
sects.Mensah and Khan [17]report that alfalfa
could be incorporated into an IPM system to con-
trol green mirids,Creontiades dilutus (Stal),on
cotton.When alfalfa was interplanted with com-
mercial cotton under an IPM regime which had no
insecticide sprays against green mireds,numbers
were reduced to levels similar to those achieved by
nine conventional insecticide sprays.The integra-
tion of an alfalfa/cotton interplant system retained
and increased populations of predatory insects in
the cotton crop[18~20].
In this study,species richness,richness index
and diversity of natural enemy community were
higher in cotton-alfalfa intercropping fields on al-
falfa-cutting than non alfalfa-cutting.This implied
that natural enemy community abundance and di-
versity in cotton field could be increased by inter-
cropping and cutting alfalfa belt at proper time.
Cutting alfalfa belts could affect the population dy-
namics of A.variegata,P.astrigera,C.sinica
and O.minutus.Cutting the alfalfa belt during the
A.gossypii population increase,the population
density of A.variegata,P.astrigera,C.sinica
and O.minutus had been increased and A.gossy-
pii had been decreased rapidly.This technique
could control the outbreak of A.gossypiiin cotton
fields effectively.The impact of alfalfa-cutting on
predators and cotton aphids was evident for about
50days.This procedure effectively forces preda-
tors from the alfalfa strips into the nearby cotton
field to control cotton aphids.
Acknowledgments
The authors thank Dunhuang Agricultural
Technology Extension Center of Gansu Province
for taking part in the field investigation.This
work was supported by the funds of Research Pro-
grams of Operating Expenses for Science of Gansu
Province,China(QS031-C31-14).
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